Warm Mix Asphalt (WMA) and Recycled Asphalt Pavement (RAP) · Warm Mix Asphalt (WMA) and Recycled...
Transcript of Warm Mix Asphalt (WMA) and Recycled Asphalt Pavement (RAP) · Warm Mix Asphalt (WMA) and Recycled...
Warm Mix Asphalt (WMA) and Recycled Asphalt Pavement (RAP)
Andrew Wrucke, M.S.C.E., E.I.
Design and Construction Engineer
Cass County, ND
Project SC-0910(062)
• Cass Highway 26 from State Highway 38 to Cass Highway 5 North
• Graded in 1993 • Originally surfaced in 1994 (planned first overlay) • Planned 2.5” asphalt overlay (≈26,000 tons) • Length: 8 Miles • March 23, 2012 NDDOT bid opening • Engineer’s estimate: $2,055,944.15 • Original low bid: $2,170,430.85 • First Superpave project in Cass County
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Project SC-0910(062) SC-0910(062)
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Project SC-0910(062)
• Original road section: 2-12’ lanes, 6’ gravel shoulder
• Overlay to include 6’ shoulders to create 36’ asphalt road top
• Designed as a standard Hot Mix Asphalt (HMA) project
– All PG 58-28 Asphalt
• NDDOT Specification 410
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HOW WE GOT TO WMA/RAP
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How we got to WMA/RAP
• Traditional bid process through NDDOT
– Low bidder: Knife River Materials; Bemidji, MN
• First project with Knife River Materials
– Had done several RAP/WMA projects in MN
– Last HMA project was several years previous
• Had viewed KR project in Norman County, MN in 2010
– Demonstration WMA/RAP project
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How we got to WMA/RAP
• Pre-Construction Conference – May 30, 2012
– Section 104.08 “Value Engineering” • Contractor allowed for use of WMA at bid price
• Contractor suggested use of RAP (initial suggestion of 20% ± 5%) in mix
• RAP source to be 1” milling of existing road
• Re-quoted milling cost from subcontractor
• Lowered gravel shoulders 1”
• Estimated cost savings: $200,000
– Completed NDDOT Change Order mid-July, 2012
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How we got to WMA/RAP
• Minnesota specifications differ greatly from ND
– Allows from oil from any source (RAP, RAS)
• Allows for RAP to be from any source, not just existing road
– Required to have 70% new oil in mix
• Allows for 25-35% RAP in mix depending on RAP AC
• Required on highly polymerized asphalts to lower RAP content (i.e. 20% max RAP on PG 58-34)
– Do not pay for oil separate of mix
– Mix tested off the road for AC content and gradation
• Allows for on the fly adjustments to final product
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CONSTRUCTION
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• Project started July 30, 2012
– Initially widening gravel shoulders with class 5 aggregate
– Existing road milled simultaneously
– RAP stockpiled at asphalt plant/pit location in Sibley, ND
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• Paving started August 1, 2012
– 1” Leveling course 26’ wide
– 1.5” wear course with 2.5” shouldering 36’ wide
• Started wear course August 2, 2012
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• Single extraction of RAP mix taken before project started by contractor for mix design
– Cores taken from several locations to gather extraction and mix design samples
• Only additional test was single sieve analysis of RAP millings to verify nominal size
• Normal NDDOT Superpave specification testing followed
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SC-0910(062)
• QA/QC Asphalt testing
– Virgin aggregate testing conducted every day by both QA/QC
– Additional worksheet filled out assure correct amount of RAP added to mixture
– Asphalt samples removed behind paver for Rice and Gyratory testing
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• Lowered add AC% from 5.6 to 4.3
– RAP had AC% of 6.3%
– Target AC% of Mix Design at 5.6%
– Resulted in 30% decrease in added AC%
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• Asphalt plant modifications
– Asphalt foamer by Maxam
• AQUABlack foamer installed on existing drum plants
• Water only added to mix, no additional chemicals
– RAP insertion point
• RAP collar added to plant by manufacturer
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• Paving operations completed August 9, 2012
• Project completed August 10, 2012
• Final Project cost: $1,872,680.43
• Savings from initial bid: $297,750.42
– Total of 13.7% Savings
– Biggest savings in PG 58-28 and Class 5
– 66% and 72% original quantity
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PROJECT REVIEW
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Project Review
• WMA technology – Cores hit compaction requirements
• NDDOT cores between 91-96%
– Paving Ambient temperature 80F-90F
– Lower WMA temperature allowed for better cooling • HMA project earlier in season had shoving and cooling
issues in hot weather
• WMA started at lower temperatures, less time required to reach workable temperatures
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Project Review
• Foamer technology used for WMA – Water added to asphalt at plant to create asphalt
emulsion • Water required to be potable and free of debris
– Lower energy costs since less heating required to coat aggregate
– Allows for lower temperatures of mixing and hauling
– Lower temperatures results in better mixture with RAP with less reheating of aged bitumen
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Project Review
• Excited by Possibilities of RAP – Costs savings of over 10% by using RAP
– 1” milling removed damaged layer of asphalt from roadway • With 1” depth removal, structure of roadway not
compromised
• Removed rutting layer, equalized rate of application
– Milling removed crack seal from roadway • Had problems with the crack seal activating in heat and
causing cracks to reflect through on previous projects
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Project Review
• RAP future savings
– Average oil cost (2012 ND): $642/ton
– AC savings from RAP: 30%
– Savings of $8.35/ton of bituminous material
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Project Review
• Road up for chip seal in 2013 or 2014, pending funds
– County regularly chip seals 2 years after overlay to increase life of pavement
– Chip seal after 2 years to add oil to RAP mixture and keep mix flexible
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FUTURE USE OF WMA/RAP
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Future Use of WMA/RAP
• New project bid by CCHD using RAP
– Cass County Highway 4 bituminous surfacing
– 40,000+ Tons of RAP in stockpile from removing existing road
– Requiring use of stockpile to create 20% ± 5% RAP mixture for bituminous surfacing
– Project bid opening on Feb 21, 2013.
• Central Specialties low bid
• $3,390,000 (46,000 ton project)
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Future use of WMA/RAP
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Future Use of WMA/RAP
• NDDOT Specification includes section on Recycled Pavements
– NDDOT Specification Section 407
– Built internal plan note referencing specification for use on future projects
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Future Use of WMA/RAP
• Allowing use of WMA on future bituminous surfacing/overlay projects
– Created note for county paving projects allowing use of WMA at Contractor’s discretion
– Some contractors in area not retrofitted for WMA yet
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Questions?